According to the Z-Way documentation the URL below should turn on a binary switch (device 20, instance 1 do obviously exist), but it doesn't... It just returns a fairly large JSON output with pretty much all the controller data...

Just to say that I have been looking everywhere to find either:
a) How to authenticate ZWaveAPI from Python so I can issue commands via the ZWayAPI
or
b) How to disable ZWaveAPI authentication.

Although the above post solved (b) - many thanks for that - I want to say how difficult this setting is to find. I would never have come across it if I hadn't stumbled across this post. Why is the setting not put in a more obvious place?

As for (a), and again after hours of searching, I have managed part of this. I have the Cookie. But I have no idea what to do with it in order to get past the "Not logged in" scenario. Being an amateur, I find much of the suggestions incomprehensible, and difficult to implement. Zway should publish the Python code to do this. My code is (short and simple):

However, as I have a Raspberry Pi operating on my private network at home, I have opted for solution (b) - disable authentication. My ZWave network has been running like this for years before I upgraded the "firmware", so it is not a problem.